You might want to be careful using wiring diagrams, descriptions etc for Z-Cars other than for your 240...the electrical system details change not only from model to model but sometimes the factory changed things during a same-year model run!
...color codes change on the wires...connectors change on the same parts, etc...
and ConorP is right on about the meter...and IMHO if you want to do your own work (and save many $$$$) get a book on car electrical systems and learn the "why" and the "how" of the basics...talk to your friends (a six-pack helps)...and don't fry those old/fragile wires...and don't be put off by thinking that
electrical systems are intimidating...they're not...but they ARE rational and problems can be found & solved by anyone!!!... Good Luck )